Coghlan's Four Function Whistle is a useful multi-function device that’s excellent for reading a map and orienteering. It features 4 key functions that are helpful in navigating the outdoors. It includes a built-in compass and whistle that's loud enough to alert others of your presence. On the back of the whistle is a thermometer that accurately tells the temperature. Inside is a magnifier that is useful for reading maps or viewing details on items. The Four Function Whistle also includes a convenient clip to attach to a zipper, belt, lanyard or backpack.